# Flags

Picture this: in your first build you start a game introducing some characters (let's call them A and B), and you add a choice menu to figure out who to eat with. "Heh, easy, let's build it right now", you say.

menu:
    "Go with A":
        A happy "Oh, yes, I know a nice place we can go..."
    "Go with B":
        B happy "Alright that's what I'm talking about!"

Game gets published on Itch, all is good. And then for build 2, you decide you want to have the main character go watch a movie with someone based on whether you ate with A or with B. So then you add a new variable, chap1_eat, and assign it as follows:

# Out of label
default chap1_eat = ""

# In label
menu:
    "Go with A":
        $ chap1_eat = "A"
        A happy "Oh, yes, I know a nice place we can go..."
    "Go with B":
        $ chap1_eat = "B"
        B happy "Alright that's what I'm talking about!"

# In another label in chapter 1
A "Oh, two tickets to the new movie!"
if chap1_eat == "A":
    B sad "But I guess you'll be going with A anyways."
elif chap1_eat == "B":
    B happy "Of course you're going with me, right?"

So now your gameflow looks a little like this:

graph LR
    A{Eat with...} -->|A| B(chap1_eat=A)
    A -->|B| C(chap1_eat=B)
    B-->D[Tickets]
    C-->D
    D-->|if chap1_eat=A| E[Go with A]
    D-->|if chap1_eat=B| F[Go with B]
    E-->G
    F-->G
    G[Sleep]
    subgraph Chapter 1
    A
    B
    C
    end
    subgraph Chapter 2
    D
    E
    F
    G
    end

(I do not personally use capital letters for Character definitions, this is for clarity.)

Nice. Now it's time to publish! Everyone's gonna love the game! ...a day later your Itch page is filled with the following screenshot:

What? Why? But I totally defined a default value for that variable! ...yes, but the variable only gets applied to a new game. All your players who tried build 1 and updated to build 2 don't have chap1_eat as a variable in their default store. You may think, ah fine, I can use the after_load label to fix this!

label after_load:
    # fixing the eating choice error with a default value
    $ chap1_eat = ""
    return

You publish the game's fix, and all is good. The next day, more comments come in: "I didn't go to see the movie. I went straight to bed." What?!

graph LR
    A{Eat with...} -->|A| B(chap1_eat=A)
    A -->|B| C(chap1_eat=B)
    B-->D[Tickets]
    C-->D

graph LR
    D[Tickets]
    D-->|if chap1_eat=A| E[Go with A]
    D-->|if chap1_eat=B| F[Go with B]
    E-->G
    F-->G
    G[Sleep]

graph LR
    A{Eat with...} -->|A| B(A)
    A -->|B| C(B)
    B-->D[Tickets, chap1_eat not defined]
    C-->D

graph LR
    H["after_load, chap1_eat="""]-->D
    D[Tickets]
    D-->|if chap1_eat=A| E["Go with A"]
    D-->|if chap1_eat=B| F["Go with B"]
    D==>|if chap1_eat=ANYTHING ELSE| G
    E-->G
    F-->G
    G[Sleep]
    style E fill:#bbf,stroke:#f66,stroke-width:3px,color:#fff,stroke-dasharray: 5 5
    style F fill:#bbf,stroke:#f66,stroke-width:3px,color:#fff,stroke-dasharray: 5 5